The present invention generally relates to equipment for dispensing dry solid particles, and to agitation systems therefor. More particularly, the present invention relates to agitation units and systems capable of use in broadcast spreaders and other dispensing equipment.
Broadcast spreaders encompass a variety of dispensing equipment that are commonly used to spread (broadcast) dry particulate or granular materials, nonlimiting examples of which include fertilizers and seeds. As a matter of convenience, these and other types of dry particulate and granular materials will hereinafter be simply referred to as granular materials. Common types of broadcast spreaders comprise a hopper having one or more outlet passageways through which the granular material drops from the hopper onto a dispersion impeller (platter) located beneath the hopper. The impeller is rotated so that material dropped onto its upper surface is spread on surfaces surrounding the spreader. Due to the presence of a rotating impeller to broadcast the granular material, such spreaders are commonly referred to as rotary spreaders and are capable of broadcasting a wide variety of granular materials. Notable examples of rotary spreaders include those described in U.S. Pat. Nos. 6,336,600 and 7,954,573, PermaGreen® Ride-On Spreader Sprayers commercially available from Perma-Green Supreme, Inc., and LESCO® brand spreaders commercially available from various retail outlets.
Oscillating agitation systems and rotary agitation systems are well known and commercially available for rotary spreaders. For example, U.S. Pat. No. 280,437 to Armstrong discloses a downwardly-extending horizontally-rotating agitator arm that passes in close proximity to an outlet passageway of a hopper through which a dry granular material drops from the hopper onto a spinning platter. Another example is described in U.S. Pat. No. 3,406,915 to Dweyer, which discloses an agitation unit with extensions that extend downward, passing close to but not entering an outlet passageway in a hopper.
While providing a level of agitation above outlet passageways, the agitators noted above have well known shortcomings. For example, fertilizer is hydroscopic and absorbs moisture from the air causing it to stick together and form clumps that clog or bridge over the passageways below the agitator extensions and within the outlet passageways themselves. Furthermore, during agitation all agitators abrade the material being agitated and create a fine dust that may further aggravate bridging and clogging problems within the outlet passageways of the hopper. A partially bridged or completely clogged outlet passageway causes an uneven output and application of the material causing unsightly results. Furthermore, once clogged the hopper may have to be emptied to clear the clog, consuming valuable time.
Rotary agitators have additional well-known problems resulting from the agitator extension traveling in a complete circular path, such that the extension contacts more of the granular material and is likely to cause more abrasion of the material than occurs with oscillating agitators. As a result, rotary agitators tend to produce more fine dust and small particles that can build up within the outlet passageways of a hopper.
It should be clear from the above description that it would be desirable if an agitation system were available that was capable of reducing clogging of a dry granular material being dispensed by a device and thereby promote flow-through of the material.